The trial of the US R&B singer R. Kelly has begun at a court in Brooklyn, New York.
The star is accused of racketeering, sexual abuse and bribery; charges which he has repeatedly denied.
Some of the allegations made against the singer - whose full name is Robert Sylvester Kelly - date back more than 20 years.
If he is convicted on all counts he could be sentenced to several decades in prison.
The first witness, Jerhonda Johnson Pace, told the jury R. Kelly knew she was underage in 2009 when they had intercourse in Chicago, where the age of consent is 17.
Now 28, she testified that she had initially told Mr Kelly she was 19, but had revealed her real age on the day they had sex for the first time.
"I felt uncomfortable. I felt like it wasn't right, that I should tell him my age.
"He asked me, 'What is that supposed to mean?' and told me to tell everyone I was 19 - and to act 21," said Ms Pace, who admits she had once been a fan of the singer.
Mr Kelly faces charges that he was the ringleader of a two-decade-long scheme where he recruited women and underage girls for sex.
In her opening argument, Mr Kelly's lawyer Nicole Blank Becker claimed the alleged victims are aggrieved groupies, who originally consented to sex before later becoming "spiteful".
"He didn't recruit them. They were fans. They came to Mr Kelly," she told the court, adding that some of the relationships were "beautiful" and "long-term".
Ms Becker portrayed her client as a victim of women, saying some enjoyed the "notoriety of being able to tell their friends that they were with a superstar".
Prosecutors meanwhile described Mr Kelly as "a man who used lies, manipulation, threats and physical abuse to dominate his victims and to avoid accountability for years".
"This case is about a predator," Assistant US Attorney Maria Melendez said in her opening statement.
"This case is not about a celebrity who likes to party a lot."
The Grammy-winning artist - wearing a grey suit, purple tie, and glasses - sat silently, his head down at times as the prosecution opened its case.
Ms Melendez said Mr Kelly's celebrity status meant he "had his pick of young fans" and that he hoarded his victims "like objects" and used "every trick in the predator handbook".
Ms Melendez alleged the singer used bodyguards, drivers, lawyers and accountants to cover up his alleged crimes.
She also said he bribed victims by photographing and filming them having sex and then threatening to release the tapes.
Mr Kelly is accused of requiring victims to demonstrate "absolute commitment" and obey strict rules, including that they eat or go to the bathroom only with his permission, not look at other men, and call him "Daddy".
The trial, delayed several times by the pandemic and predicted to last about one month, is expected to include testimony from some female accusers and at least one male accuser.
Even if he is acquitted, Mr Kelly still faces sex-related charges in Illinois and Minnesota, where he has also pleaded not guilty.
Mr Kelly has been in jail for the last two years. He was moved in June to Brooklyn from Chicago for the trial.
The singer is best known for hits including Ignition (Remix), I Believe I Can Fly, Bump n' Grind and If I Could Turn Back the Hands of Time.
On her way into the court, BBC producer Monica Miller reported seeing supporters of the singer shouting "Free R. Kelly".